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Almyras, G., Sangiovanni, D. G. & Sarakinos, K. (2019). Semi-Empirical Force-Field Model For The Ti1-XAlXN (0 ≤ x ≤ 1) System. Materials, 12(2), Article ID 215.
Open this publication in new window or tab >>Semi-Empirical Force-Field Model For The Ti1-XAlXN (0 ≤ x ≤ 1) System
2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 2, article id 215Article in journal (Refereed) Published
Abstract [en]

We present a modified embedded atom method (MEAM) semi-empirical force-field model for the Ti1-xAlxN (0 x 1) alloy system. The MEAM parameters, determined via an adaptive simulated-annealing (ASA) minimization scheme, optimize the models predictions with respect to 0 K equilibrium volumes, elastic constants, cohesive energies, enthalpies of mixing, and point-defect formation energies, for a set of approximate to 40 elemental, binary, and ternary Ti-Al-N structures and configurations. Subsequently, the reliability of the model is thoroughly verified against known finite-temperature thermodynamic and kinetic properties of key binary Ti-N and Al-N phases, as well as properties of Ti1-xAlxN (0 amp;lt; x amp;lt; 1) alloys. The successful outcome of the validation underscores the transferability of our model, opening the way for large-scale molecular dynamics simulations of, e.g., phase evolution, interfacial processes, and mechanical response in Ti-Al-N-based alloys, superlattices, and nanostructures.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
titanium-aluminum nitride; Ti-Al-N; MD simulations; molecular dynamics; interatomic potential; MEAM; force-field model; spinodal decomposition; phase stability
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:liu:diva-155607 (URN)10.3390/ma12020215 (DOI)000459719000019 ()30634593 (PubMedID)
Note

Funding Agencies|Olle Engkvist foundation; competence center FunMat-II - Vinnova [2016-05156]; Linkoping University ("LiU Career Contract") [LiU-2015-01510]; Swedish research council [VR-2015-04630]; Olle Engkvist foundation [SOEB 190-312]

Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-05-14
Elofsson, V., Almyras, G., Lü, B., Garbrecht, M., Boyd, R. & Sarakinos, K. (2018). Structure formation in Ag-X (X = Au, Cu) alloys synthesized far-from-equilibrium. Journal of Applied Physics, 123(16)
Open this publication in new window or tab >>Structure formation in Ag-X (X = Au, Cu) alloys synthesized far-from-equilibrium
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2018 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, no 16Article in journal (Refereed) Published
Abstract [en]

We employ sub-monolayer, pulsed Ag and Au vapor fluxes, along with deterministic growth simulations, and nanoscale probes to study structure formation in miscible Ag-Au films synthesized under far-from-equilibrium conditions. Our results show that nanoscale atomic arrangement is primarily determined by roughness build up at the film growth front, whereby larger roughness leads to increased intermixing between Ag and Au. These findings suggest a different structure formation pathway as compared to the immiscible Ag-Cu system for which the present study, in combination with previously published data, reveals that no significant roughness is developed, and the local atomic structure is predominantly determined by the tendency of Ag and Cu to phase-separate.

Place, publisher, year, edition, pages
New York: A I P Publishing LLC, 2018
National Category
Inorganic Chemistry Other Physics Topics Atom and Molecular Physics and Optics Condensed Matter Physics Physical Chemistry
Identifiers
urn:nbn:se:liu:diva-147730 (URN)10.1063/1.5018907 (DOI)000431147200150 ()
Note

Funding agencies: Linkoping University via the "LiU Research Fellows Program"; Linkoping University via the "LiU Career Contract" [Dnr-LiU-2015-01510]; Swedish Research Council [VR-2011-5312, VR-2015-04630]

Available from: 2018-05-08 Created: 2018-05-08 Last updated: 2018-05-31Bibliographically approved
Chason, E., Karlson, M., Colin, J. J., Magnfält, D., Sarakinos, K. & Abadias, G. (2016). A kinetic model for stress generation in thin films grown from energetic vapor fluxes. Journal of Applied Physics, 119(14), Article ID 145307.
Open this publication in new window or tab >>A kinetic model for stress generation in thin films grown from energetic vapor fluxes
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2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 14, article id 145307Article in journal (Refereed) Published
Abstract [en]

We have developed a kinetic model for residual stress generation in thin films grown from energetic vapor fluxes, encountered, e.g., during sputter deposition. The new analytical model considers sub-surface point defects created by atomic peening, along with processes treated in already existing stress models for non-energetic deposition, i.e., thermally activated diffusion processes at the surface and the grain boundary. According to the new model, ballistically induced subsurface defects can get incorporated as excess atoms at the grain boundary, remain trapped in the bulk, or annihilate at the free surface, resulting in a complex dependence of the steady-state stress on the grain size, the growth rate, as well as the energetics of the incoming particle flux. We compare calculations from the model with in situ stress measurements performed on a series of Mo films sputter-deposited at different conditions and having different grain sizes. The model is able to reproduce the observed increase of compressive stress with increasing growth rate, behavior that is the opposite of what is typically seen under non-energetic growth conditions. On a grander scale, this study is a step towards obtaining a comprehensive understanding of stress generation and evolution in vapor deposited polycrystalline thin films. Published by AIP Publishing.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2016
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:liu:diva-130444 (URN)10.1063/1.4946039 (DOI)000379161100035 ()
Note

Funding Agencies|U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) [DE-SC0008799]; Linkoping University (LiU) [Dnr-LiU-2015-01510]

Available from: 2016-08-06 Created: 2016-08-05 Last updated: 2017-11-28
Elofsson, V., Almyras, G., Lu, B., Boyd, R. & Sarakinos, K. (2016). Atomic arrangement in immiscible Ag-Cu alloys synthesized far-from-equilibrium. Acta Materialia, 110, 114-121
Open this publication in new window or tab >>Atomic arrangement in immiscible Ag-Cu alloys synthesized far-from-equilibrium
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2016 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 110, p. 114-121Article in journal (Refereed) Published
Abstract [en]

Physical attributes of multicomponent materials of a given chemical composition are determined by atomic arrangement at property-relevant length scales. A potential route to access a vast array of atomic configurations for material property tuning is by synthesis of multicomponent thin films using vapor fluxes with their deposition pattern modulated in the sub-monolayer regime. However, the applicability of this route for creating new functional materials is impeded by the fact that a fundamental understanding of the combined effect of sub-monolayer flux modulation, kinetics and thermodynamics on atomic arrangement is not available in the literature. Here we present a research strategy and verify its viability for addressing the aforementioned gap in knowledge. This strategy encompasses thin film synthesis using a route that generates multi-atomic fluxes with sub-monolayer resolution and precision over a wide range of experimental conditions, deterministic growth simulations and nanoscale micro structural probes. Investigations are focused on structure formation within the archetype immiscible Ag-Cu binary system, revealing that atomic arrangement at different length scales is governed by the arrival pattern of the film forming species, in conjunction with diffusion of near-surface Ag atoms to encapsulate 3D Cu islands growing on 2D Ag layers. The knowledge generated and the methodology presented herein provides the scientific foundation for tailoring atomic arrangement and physical properties in a wide range of miscible and immiscible multinary systems. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2016
Keywords
Ag-Cu thin films; MD simulations; Modulated vapor fluxes; Nonequilibrium synthesis; Immiscible alloys
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-128722 (URN)10.1016/j.actamat.2016.03.023 (DOI)000374810400012 ()
Note

Funding Agencies|Linkoping University [Dnr-LiU-2015-01510]; Swedish Research Council [VR 621-2011-5312]; AForsk through the project "Towards Next Generation of Energy Saving Windows"

Available from: 2016-06-01 Created: 2016-05-30 Last updated: 2018-03-23
Magnfält, D., Fillon, A., Boyd, R., Helmersson, U., Sarakinos, K. & Abadias, G. (2016). Compressive intrinsic stress originates in the grain boundaries of dense refractory polycrystalline thin films. Journal of Applied Physics, 119(5), 055305
Open this publication in new window or tab >>Compressive intrinsic stress originates in the grain boundaries of dense refractory polycrystalline thin films
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2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 5, p. 055305-Article in journal (Refereed) Published
Abstract [en]

Intrinsic stresses in vapor deposited thin films have been a topic of considerable scientific and technological interest owing to their importance for functionality and performance of thin film devices. The origin of compressive stresses typically observed during deposition of polycrystalline metal films at conditions that result in high atomic mobility has been under debate in the literature in the course of the past decades. In this study, we contribute towards resolving this debate by investigating the grain size dependence of compressive stress magnitude in dense polycrystalline Mo films grown by magnetron sputtering. Although Mo is a refractory metal and hence exhibits an intrinsically low mobility, low energy ion bombardment is used during growth to enhance atomic mobility and densify the grain boundaries. Concurrently, the lateral grain size is controlled by using appropriate seed layers on which Mo films are grown epitaxially. The combination of in situ stress monitoring with ex situ microstructural characterization reveals a strong, seemingly linear, increase of the compressive stress magnitude on the inverse grain size and thus provides evidence that compressive stress is generated in the grain boundaries of the film. These results are consistent with models suggesting that compressive stresses in metallic films deposited at high homologous temperatures are generated by atom incorporation into and densification of grain boundaries. However, the underlying mechanisms for grain boundary densification might be different from those in the present study where atomic mobility is intrinsically low. (C) 2016 AIP Publishing LLC.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-125810 (URN)10.1063/1.4941271 (DOI)000369900600028 ()
Note

Funding Agencies|COST Action "Highly Ionized Pulsed Plasmas" [MP0804]; Swedish Research Council VR [621-2014-4882]; Linkoping University via the "LiU Research Fellows" program.

The previous status of this article was Manuscript and the working title was Atom insertion into grain boundaries generates compressive intrinsic stress in polycrystalline thin films.

Available from: 2016-03-08 Created: 2016-03-04 Last updated: 2017-11-30Bibliographically approved
Sarakinos, K., Greczynski, G., Elofsson, V., Magnfält, D., Högberg, H. & Alling, B. (2016). Theoretical and experimental study of metastable solid solutions and phase stability within the immiscible Ag-Mo binary system. Journal of Applied Physics, 119(9), 095303
Open this publication in new window or tab >>Theoretical and experimental study of metastable solid solutions and phase stability within the immiscible Ag-Mo binary system
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2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 9, p. 095303-Article in journal (Refereed) Published
Abstract [en]

Metastable solid solutions are phases that are synthesized far from thermodynamic equilibrium and offer a versatile route to design materials with tailor-made functionalities. One of the most investigated classes of metastable solid solutions with widespread technological implications is vapor deposited ternary transition metal ceramic thin films (i.e., nitrides, carbides, and borides). The vapor-based synthesis of these ceramic phases involves complex and difficult to control chemical interactions of the vapor species with the growing film surface, which often makes the fundamental understanding of the composition-properties relations a challenging task. Hence, in the present study, we investigate the phase stability within an immiscible binary thin film system that offers a simpler synthesis chemistry, i.e., the Ag-Mo system. We employ magnetron co-sputtering to grow Ag1-xMox thin films over the entire composition range along with x-ray probes to investigate the films structure and bonding properties. Concurrently, we use density functional theory calculations to predict phase stability and determine the effect of chemical composition on the lattice volume and the electronic properties of Ag-Mo solid solutions. Our combined theoretical and experimental data show that Mo-rich films (x >= similar to 0.54) form bcc Mo-Ag metastable solid solutions. Furthermore, for Ag-rich compositions (x <= similar to 0.21), our data can be interpreted as Mo not being dissolved in the Ag fcc lattice. All in all, our data show an asymmetry with regards to the mutual solubility of Ag and Mo in the two crystal structures, i.e., Ag has a larger propensity for dissolving in the bcc-Mo lattice as compared to Mo in the fcc-Ag lattice. We explain these findings in light of isostructural short-range clustering that induces energy difference between the two (fcc and bcc) metastable phases. We also suggest that the phase stability can be explained by the larger atomic mobility of Ag atoms as compared to that of Mo. The mechanisms suggested herein may be of relevance for explaining phase stability data in a number of metastable alloys, such as ternary transition metal-aluminum-nitride systems. (C) 2016 AIP Publishing LLC.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-127275 (URN)10.1063/1.4942840 (DOI)000372351900057 ()
Note

Funding Agencies|Linkoping University [Dnr-LiU-2015-01510]; Swedish Research Council (VR) [621-2011-4417, 330-2014-6336]; VINN Excellence Center Functional Nanoscale Materials (FunMat); Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]

Available from: 2016-04-20 Created: 2016-04-19 Last updated: 2017-11-30Bibliographically approved
Lü, B., Münger, P. & Sarakinos, K. (2015). Coalescence-controlled and coalescence-free growth regimes during deposition of pulsed metal vapor fluxes on insulating surfaces. Journal of Applied Physics, 117(13), Article ID 134304.
Open this publication in new window or tab >>Coalescence-controlled and coalescence-free growth regimes during deposition of pulsed metal vapor fluxes on insulating surfaces
2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 13, article id 134304Article in journal (Refereed) Published
Abstract [en]

The morphology and physical properties of thin films deposited by vapor condensation on solid surfaces are predominantly set by the processes of island nucleation, growth, and coalescence. When deposition is performed using pulsed vapor fluxes, three distinct nucleation regimes are known to exist depending on the temporal profile of the flux. These regimes can be accessed by tuning deposition conditions; however, their effect on film microstructure becomes marginal when coalescence sets in and erases morphological features obtained during nucleation. By preventing coalescence from being completed, these nucleation regimes can be used to control microstructure evolution and thus access a larger palette of film morphological features. Recently, we derived the quantitative criterion to stop coalescence during continuous metal vapor flux deposition on insulating surfaceswhich typically yields 3-dimensional growthby describing analytically the competition between island growth by atomic incorporation and the coalescence rate of islands [Lu et al., Appl. Phys. Lett. 105, 163107 (2014)]. Here, we develop the analytical framework for entering a coalescence-free growth regime for metal vapor deposition on insulating substrates using pulsed vapor fluxes, showing that there exist three distinct criteria for suppressing coalescence that correspond to the three nucleation regimes of pulsed vapor flux deposition. The theoretical framework developed herein is substantiated by kinetic Monte Carlo growth simulations. Our findings highlight the possibility of using atomistic nucleation theory for pulsed vapor deposition to control morphology of thin films beyond the point of island density saturation. (C) 2015 AIP Publishing LLC.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2015
National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:liu:diva-117792 (URN)10.1063/1.4916983 (DOI)000352645100033 ()
Note

Funding Agencies|Linkoping University via the "LiU Research Fellows" program; Swedish Research Council [VR 621-2011-5312]; AForsk through the project "Towards Next Generation Energy Saving Windows"

Available from: 2015-05-11 Created: 2015-05-08 Last updated: 2018-03-13
Sarakinos, K., Magnfält, D., Elofsson, V. & Lü, B. (2014). Atomistic view on thin film nucleation and growth by using highly ionized and pulsed vapour fluxes. Surface & Coatings Technology, 257, 326-332
Open this publication in new window or tab >>Atomistic view on thin film nucleation and growth by using highly ionized and pulsed vapour fluxes
2014 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 257, p. 326-332Article in journal (Refereed) Published
Abstract [en]

We present a brief review on the use of ionized and pulsed vapour fluxes, primarily generated by high power impulse magnetron sputtering (HiPIMS) discharges, as tools to gain atomistic understanding on film nucleation and growth. Two case studies are considered; the first case study concerns stress generation in polycrystalline films. It is highlighted that by using vapour fluxes of well-controlled ion content and ion energy and by studying the film microstructure and intrinsic stresses one can obtain experimental evidence for stress generation by insertion of film forming species in the grain boundaries. In the second case study it is discussed how the use of pulsed vapour fluxes with well controlled time domain can facilitate understanding of growth dynamics and microstructural evolution in thin films grown in three-dimensional (i.e., Volmer-Weber) fashion. Broader implications of the described research strategies for the surface science and surface engineering communities are highlighted and discussed.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Film nucleation and growth; In situ growth monitoring; Intrinsic stresses; Volmer-Weber film growth; HiPIMS; Microstructure
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-112642 (URN)10.1016/j.surfcoat.2014.04.015 (DOI)000344423100032 ()
Note

Funding Agencies|Linkoping University through the "LiU Research Fellows" programme; Swedish Research Council [VR 621-2001-5312]; Angpanneforeningens Forskningsstiftelse through the project "Towards Next Generation Energy Saving Windows"

Available from: 2014-12-05 Created: 2014-12-05 Last updated: 2017-12-05Bibliographically approved
Sønderby, S., Aijaz, A., Helmersson, U., Sarakinos, K. & Eklund, P. (2014). Deposition of yttria-stabilized zirconia thin films by high power impulse magnetron sputtering and pulsed magnetron sputtering. Surface & Coatings Technology, 240, 1-6
Open this publication in new window or tab >>Deposition of yttria-stabilized zirconia thin films by high power impulse magnetron sputtering and pulsed magnetron sputtering
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2014 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 240, p. 1-6Article in journal (Refereed) Published
Abstract [en]

Yttria-stabilized zirconia (YSZ) thin films were reactively sputter-deposited by high power impulse magnetron sputtering (HiPIMS) and pulsed direct current magnetron sputtering (DCMS). The use of substrate bias voltage was studied in both modes of deposition as a process parameter to promote the growth of dense and less columnar films. Films were deposited on both Si(100) and NiO-YSZ fuel cell anodes. The texture, morphology and composition of the deposited films were investigated with regard to their application as thin electrolytes for solid oxide fuel cells (SOFCs). Independent of the deposition mode the films were found to be stoichiometric. The application of substrate bias voltage had opposite effects on texture and crystallinity of films deposited by pulsed DCMS and HiPIMS. Films deposited by pulsed DCMS became highly crystalline and <220> textured at high bias voltage whereas bias applied to HiPIMS deposited films disrupted crystal growth leading to deterioration of crystallinity. Comparing film morphology, it was found that pulsed DCMS films were columnar and contained voids regardless of the applied substrate bias. When depositing by HiPIMS a window of operation at a bias voltage of -25 V to -50 V was found in which it is possible to deposit non-columnar thin films without voids and cracks as desired for SOFC applications. 

Keywords
HiPIMS, HPPMS, pulsed DCMS, SOFC, YSZ, Substrate bias
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-102516 (URN)10.1016/j.surfcoat.2013.12.001 (DOI)000331989900001 ()
Available from: 2013-12-12 Created: 2013-12-12 Last updated: 2017-12-06
Elofsson, V., Saraiva, M., Boyd, R. & Sarakinos, K. (2014). Double in-plane alignment in biaxially textured thin films. Applied Physics Letters, 105(23), 233113
Open this publication in new window or tab >>Double in-plane alignment in biaxially textured thin films
2014 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 23, p. 233113-Article in journal (Refereed) Published
Abstract [en]

The scientific interest and technological relevance of biaxially textured polycrystalline thin films stem from their microstructure that resembles that of single crystals. To explain the origin and predict the type of biaxial texture in off-normally deposited films, Mahieu et al. have developed an analytical model [S. Mahieu et al., Thin Solid Films 515, 1229 (2006)]. For certain materials, this model predicts the occurrence of a double in-plane alignment, however, experimentally only a single in-plane alignment has been observed and the reason for this discrepancy is still unknown. The model calculates the resulting in-plane alignment by considering the growth of faceted grains with an out-of-plane orientation that corresponds to the predominant film out-of-plane texture. This approach overlooks the fact that in vapor condensation experiments where growth kinetics is limited and only surface diffusion is active, out-of-plane orientation selection is random during grain nucleation and happens only upon grain impingement. Here, we compile and implement an experiment that is consistent with the key assumptions set forth by the in-plane orientation selection model by Mahieu et al.; a Cr film is grown off-normally on a fiber textured Ti epilayer to pre-determine the out-of-plane orientation and only allow for competitive growth with respect to the in-plane alignment. Our results show unambiguously a biaxially textured Cr (110) film that possesses a double in-plane alignment, in agreement with predictions of the in-plane selection model. Thus, a long standing discrepancy in the literature is resolved, paving the way towards more accurate theoretical descriptions and hence knowledge-based control of microstructure evolution in biaxially textured thin films.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2014
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-113499 (URN)10.1063/1.4903932 (DOI)000346266000086 ()
Note

Funding Agencies|Linkoping University

Available from: 2015-01-19 Created: 2015-01-19 Last updated: 2017-12-05
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ORCID iD: ORCID iD iconorcid.org/0000-0003-2864-9509

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